A greater understanding of how aberrant miRNA expression contributes to clinical and pathological characteristics of retinoblastoma could provide novel therapeutic targets for cancer treatment. Our long-term goal is to identify genetic changes that occur in retinoblastoma in order to effectively use that information to target therapy. The objective for this study, which is the next step toward the attainment of our long-term goal, is to establish the link between miRNA expression and retinoblastoma invasion for the identification of novel therapeutic targets. Our central hypothesis is that aberrant miR-31 expression could be instrumental in retinoblastoma invasion due to the loss of inhibition of key target genes. For this reason, miR-31 could serve as a viable target for retinoblastoma treatment. The rationale for this proposed research is that a better understanding of how aberrant miR-31 and target gene expression contribute to retinoblastoma invasion could lead to the identification of therapeutic targets for retinoblastoma, and lead to a greater understanding of the mechanisms associated with invasion and metastasis in general. We plan to test our central hypothesis by pursuing the following specific aims: (1) To define the role of miR-31 in retinoblastoma invasion. We will pursue this specific aim by analyzing miR-31 expression in human retinoblastoma tumors and isolated invasive human retinoblastoma cells. Further, miR-31 expression will be manipulated in retinoblastoma cell lines in vitro and in vivo in order to determine changes in invasive capacity. (2) To validate the potential miR-31 targets that promote invasion of retinoblastoma. We will pursue this specific aim by determining the effect of miR-31 expression on potential targets, and by measuring target protein expression in retinoblastoma cells invading the optic nerve and other intraocular structures. We will also manipulate target gene expression independently and in relation to miR-31 expression to determine changes in cell invasion. It is expected that our contribution in this proposed research study will be to provide a detailed understanding of how aberrant miRNA expression contributes to retinoblastoma invasion. This contribution will be significant because it is an important step i a continuum of research involving the identification of genetic changes within retinoblastoma that can be targeted for the development of novel therapies. The proposed research is innovative, in our opinion, because it will address two important but understudied topics: (1) Mechanisms essential to retinoblastoma invasion, and (2) How miRNAs contribute to important clinical and pathologic characteristics of retinoblastoma. The proposed research is relevant to public health because a greater understanding of how aberrant miRNA expression contributes to tumor progression will apply not only to retinoblastoma, but to other cancers as well. As such, what is learned from this research could provide novel targets for chemotherapeutic intervention to prevent or slow the progression to metastatic retinoblastoma. Further, this knowledge could provide new insights into the mechanisms associated with tumor invasion and metastasis across cancer types.